Subject: Re: [RFC/PATCH] Implement {read,update}_persistent_clock. v2

From: [email-masked] (Tony Breeds)
Date: Tue, 11 Sep 2007 18:17:46 +1000

From: Tony Breeds <[email-masked]>

Implement {read,update}_persistent_clock.

With these functions implemented we cooperate better with the generic
timekeeping code.  This obsoletes the need for the timer sysdev as a bonus.

Signed-off-by: Tony Breeds <[email-masked]>

---

Functionally is the same as previous version,  Just a few cleanups.

* Compile tested for arch/powerpc/configs/*_defconfig
* Booted on pSeries, iSeries, Cell and PS3
* Really needs booting on powermac and a quad G5 (hint hint)
* Should remove arch/powerpc/sysdev/timer.c

 arch/powerpc/Kconfig         |    3 +
 arch/powerpc/kernel/time.c   |   58 ++++++++++-------------------------
 arch/powerpc/sysdev/Makefile |    5 ---
 3 files changed, 20 insertions(+), 46 deletions(-)

Index: working/arch/powerpc/Kconfig
===================================================================
--- working.orig/arch/powerpc/Kconfig
+++ working/arch/powerpc/Kconfig
@@ -21,6 +21,9 @@ config MMU
 	bool
 	default y
 
+config GENERIC_CMOS_UPDATE
+	def_bool y
+
 config GENERIC_HARDIRQS
 	bool
 	default y
Index: working/arch/powerpc/kernel/time.c
===================================================================
--- working.orig/arch/powerpc/kernel/time.c
+++ working/arch/powerpc/kernel/time.c
@@ -74,16 +74,11 @@
 #endif
 #include <asm/smp.h>
 
-/* keep track of when we need to update the rtc */
-time_t last_rtc_update;
 #ifdef CONFIG_PPC_ISERIES
 static unsigned long __initdata iSeries_recal_titan;
 static signed long __initdata iSeries_recal_tb;
 #endif
 
-/* The decrementer counts down by 128 every 128ns on a 601. */
-#define DECREMENTER_COUNT_601	(1000000000 / HZ)
-
 #define XSEC_PER_SEC (1024*1024)
 
 #ifdef CONFIG_PPC64
@@ -349,39 +344,6 @@ void udelay(unsigned long usecs)
 }
 EXPORT_SYMBOL(udelay);
 
-static __inline__ void timer_check_rtc(void)
-{
-        /*
-         * update the rtc when needed, this should be performed on the
-         * right fraction of a second. Half or full second ?
-         * Full second works on mk48t59 clocks, others need testing.
-         * Note that this update is basically only used through 
-         * the adjtimex system calls. Setting the HW clock in
-         * any other way is a /dev/rtc and userland business.
-         * This is still wrong by -0.5/+1.5 jiffies because of the
-         * timer interrupt resolution and possible delay, but here we 
-         * hit a quantization limit which can only be solved by higher
-         * resolution timers and decoupling time management from timer
-         * interrupts. This is also wrong on the clocks
-         * which require being written at the half second boundary.
-         * We should have an rtc call that only sets the minutes and
-         * seconds like on Intel to avoid problems with non UTC clocks.
-         */
-        if (ppc_md.set_rtc_time && ntp_synced() &&
-	    xtime.tv_sec - last_rtc_update >= 659 &&
-	    abs((xtime.tv_nsec/1000) - (1000000-1000000/HZ)) < 500000/HZ) {
-		struct rtc_time tm;
-		to_tm(xtime.tv_sec + 1 + timezone_offset, &tm);
-		tm.tm_year -= 1900;
-		tm.tm_mon -= 1;
-		if (ppc_md.set_rtc_time(&tm) == 0)
-			last_rtc_update = xtime.tv_sec + 1;
-		else
-			/* Try again one minute later */
-			last_rtc_update += 60;
-        }
-}
-
 /*
  * This version of gettimeofday has microsecond resolution.
  */
@@ -688,7 +650,6 @@ void timer_interrupt(struct pt_regs * re
 			tb_last_jiffy = tb_next_jiffy;
 			do_timer(1);
 			timer_recalc_offset(tb_last_jiffy);
-			timer_check_rtc();
 		}
 		write_sequnlock(&xtime_lock);
 	}
@@ -800,11 +761,6 @@ int do_settimeofday(struct timespec *tv)
  	set_normalized_timespec(&xtime, new_sec, new_nsec);
 	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
 
-	/* In case of a large backwards jump in time with NTP, we want the 
-	 * clock to be updated as soon as the PLL is again in lock.
-	 */
-	last_rtc_update = new_sec - 658;
-
 	ntp_clear();
 
 	new_xsec = xtime.tv_nsec;
@@ -880,12 +836,35 @@ void __init generic_calibrate_decr(void)
 #endif
 }
 
-unsigned long get_boot_time(void)
+int update_persistent_clock(struct timespec now)
+{
+	struct rtc_time tm;
+
+	if (!ppc_md.set_rtc_time)
+		return 0;
+
+	to_tm(now.tv_sec + 1 + timezone_offset, &tm);
+	tm.tm_year -= 1900;
+	tm.tm_mon -= 1;
+
+	return ppc_md.set_rtc_time(&tm);
+}
+
+unsigned long read_persistent_clock(void)
 {
 	struct rtc_time tm;
+	static int first = 1;
+
+	if (first) {
+		first = 0;
+		if (ppc_md.time_init)
+			timezone_offset = ppc_md.time_init();
+	}
 
-	if (ppc_md.get_boot_time)
-		return ppc_md.get_boot_time();
+	/* get_boot_time() isn't guaranteed to be safe to call late */
+	/* FIXME: is the a better check available here? */
+	if (system_state != SYSTEM_RUNNING && ppc_md.get_boot_time)
+		return ppc_md.get_boot_time() -timezone_offset;
 	if (!ppc_md.get_rtc_time)
 		return 0;
 	ppc_md.get_rtc_time(&tm);
@@ -897,14 +876,10 @@ unsigned long get_boot_time(void)
 void __init time_init(void)
 {
 	unsigned long flags;
-	unsigned long tm = 0;
 	struct div_result res;
 	u64 scale, x;
 	unsigned shift;
 
-        if (ppc_md.time_init != NULL)
-                timezone_offset = ppc_md.time_init();
-
 	if (__USE_RTC()) {
 		/* 601 processor: dec counts down by 128 every 128ns */
 		ppc_tb_freq = 1000000000;
@@ -979,19 +954,14 @@ void __init time_init(void)
 	/* Save the current timebase to pretty up CONFIG_PRINTK_TIME */
 	boot_tb = get_tb();
 
-	tm = get_boot_time();
-
 	write_seqlock_irqsave(&xtime_lock, flags);
 
 	/* If platform provided a timezone (pmac), we correct the time */
         if (timezone_offset) {
 		sys_tz.tz_minuteswest = -timezone_offset / 60;
 		sys_tz.tz_dsttime = 0;
-		tm -= timezone_offset;
         }
 
-	xtime.tv_sec = tm;
-	xtime.tv_nsec = 0;
 	do_gtod.varp = &do_gtod.vars[0];
 	do_gtod.var_idx = 0;
 	do_gtod.varp->tb_orig_stamp = tb_last_jiffy;
@@ -1009,9 +979,6 @@ void __init time_init(void)
 
 	time_freq = 0;
 
-	last_rtc_update = xtime.tv_sec;
-	set_normalized_timespec(&wall_to_monotonic,
-	                        -xtime.tv_sec, -xtime.tv_nsec);
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 
 	/* Not exact, but the timer interrupt takes care of this */
Index: working/arch/powerpc/sysdev/Makefile
===================================================================
--- working.orig/arch/powerpc/sysdev/Makefile
+++ working/arch/powerpc/sysdev/Makefile
@@ -20,11 +20,6 @@ obj-$(CONFIG_MV64X60)		+= $(mv64x60-y) m
 obj-$(CONFIG_RTC_DRV_CMOS)	+= rtc_cmos_setup.o
 obj-$(CONFIG_AXON_RAM)		+= axonram.o
 
-# contains only the suspend handler for time
-ifeq ($(CONFIG_RTC_CLASS),)
-obj-$(CONFIG_PM)		+= timer.o
-endif
-
 ifeq ($(CONFIG_PPC_MERGE),y)
 obj-$(CONFIG_PPC_INDIRECT_PCI)	+= indirect_pci.o
 obj-$(CONFIG_PPC_I8259)		+= i8259.o